Froth flotation of siliceous material



Patented Aug. 18, 1942 FROTH FLOTATION F SILICEOUS MATERIAL Barry L.Mead and Ernest J. Maust, Brewster,

Fla., assignors to American Cyanamid Company, New York, N. TL, acorporation of Maine No Drawing. Application March 7, 1940, Serial No.322,771

11 Claims. (Cl. 209-166) The present invention relates to frothflotation processes for the removal of acidic siliceous gangue from orescontaining it.

Attempts have been made in the past to beneficiate ores, particularlynon-metallic ores, containing siliceous gangue by froth flotation of thesiliceous portion using promoters especially prepared for this purpose.These promoters are in general compounds having a positively chargedsurface active portion and are usually referred to as cationic reagents.Typical reagents of this type are quaternary ammonium compounds such asthose described in the Lenher U. S. Patent No. 2,132,902, for exampleCetyl trimethylammonium bromide or chloride Lauryl trimethyl ammoniumchloride or iodide Cetyl pyridinium bromide Dimethylbenzyl phenylammonium chloride sulfonatedin benzyl ring Beta diethyl amino ethyloleyl amide acetate Beta diethyl amino ethyl oleyl amide hydrochlorideTrimethyl ammonium methyl sulfate or amino oleyl ethylene diamineQuaternary ammonium compounds containing at least one aliphatic chainwith at least eight and 'not more than twenty carbon atoms in themolecule Water-soluble or acid solution soluble compounds of aminocellulose such as chitosan acetate Trimethyl octadecyl ammonium bromideTrimethyl eicosyl ammonium iodide Octadecyl pyridinium bromide Trimethyloctadecyl ammonium chloride Trimethyl dodecyl ammonium bromide Trimethyldodecyl ammonium iodide Octadecyl beta hydroxyethyl morpholinium bromideCetyl beta hydroxyethyl morpholinium bromide Triethyl Octadecyl ammoniumbromide Triethyl cetyl ammonium bromide Beta stearamidophenyltrimethylammonium methyl sulfate Octadecyl pyridinium chloride Octadecylpyridinium iodide Octadecyl alpha picolinium bromide Octadecylquinolinium bromide Dodecyl pyridinium bromide Heptadecylaminohydrochloride Hexadecylamine hydrochloride Dodecylamine hydrochlorideand the primary and secondary aliphatic amines having long hydrocarbonchains attached to the Patent No. 2,168,840 such as monoand di-hexyl,octyl and decyl amines and their water-soluble salts and mixed aminesbutyl dodecyl amine, butyl octadecyl amine and the like.

- The procedure proposed hitherto using cationic promoters for theflotation of silica give good results with ores which are slime-free andwhich do not produce slime readily. However, when slime is present, orwhen the ore readily produces slime, the effect upon flotation of silicais markedly deleterious even upon the use of excessive and prohibitiveamounts of the cationic reagent with the result that the flotation ofthe silica is very incomplete resulting in obtaining a non-floatableproduct that is unmarketable and noneconomical due to the silica itcontains.

The most important field of silica flotation at the present time ispresented by the Florida pebble phosphate deposits in which finelydivided siliceous gangue is intimately associated with the finelydivided phosphatic particles, both contained in a matrix wherein thebonding material is made up of phosphatic and aluminous clay. However,up to the present time the use of cationic reagents to effect a silicaflotation has not been commercially feasible with phosphatic ores due tothe fact that excessive reagent costs resulted or else if the amount ofreagent were reduced within commercial limits, the silica removal is notsufliciently complete to produce a high grade phosphate product. Thecopending applications Serial No. 320,121, filed February 21, 1940, andSerial No. 325,011, filed March 20, 1940, have described a process ofsilica flotation in which the ore, such as for example, a pebblephosphate ore, is subjected to an extraordinarily complete deslimingprocedure removing the last trace of existing slime. These procedureshave greatly improved the silica removal but encountered diflicultieswhen applied to materials such as certain phosphate rocks which haverelatively soft surfaces and which under the conditioning treatmentnormally preceding froth flotation, tend to disintegrate on the surfaceto form a small amount of colloidal and semi-colloidal slime. Thisslime, which is of the material which is not to be floated, appears tobe still more deleterious in its effect on silica flotation than thenative or original slime which is largely of an aluminous silicatenature, and a very small proportion of this phosphatic slime will exerta greater effect than a corresponding proportion of ordinaryargillaceous slime.

According to the present invention we have nitrogen such as thosedescribed in Amour U. S. found that if a thoroughly deslimed ore isadmitted directly to the flotation cell from its deslimlng operation ina thoroughly deslimed condition that silica can be floated from this oreeconomically if the reagents are added directly In the above table weshow that increasing amounts of silica are left behind in thenonfloatable portion as the time of asitation is increased and thatalter 30 seconds of agitation to the flotation cell and both the silicafroth and 5 a non-economical phosphate product is obtained thenon-floatable portion are removed from the from the particular oretreated due to the large cell immediately before the non-floatableportion amount of silica leit with it.

is allowed to produce a slime. In ordinary flota- 1 The presentinvention is' not intended to be tion the ore is generally conditionedin the preslimited to any particular theory of action. We ence of thereagent bef the flotation operation believe that the rapidity with whichthe cation is performed. In the use of the cationic reagents activepromoter floats silica apparently is due for the flotation of silicathis normal ndi i nat least in part to the fact that the action of theing process proves to be detrimental to the flotapromoter takes placeimmediately and leaves no tion operation in that he slime Produced funchanged promoter in the pulp because if an the non-floatable portionso effects the cationic excess of promoter is used, and t excess reagentthat the silica is inadequately floated, covered from the waterassociated with the pulp, resulting in an inferior non-floated product@011- this excess does not have the same activity. talninl; an excessiveamount of silica. After the An example of a flotation test wherein wesilica has been removed from the no added a great excess of cationicreagent and and s im producing material the silica then may attempted tofloat the silica in a second charge, be removed to a cleaning Operationt0 using the residue solution from the first charge, quent handling orflotation steps without in- 1 shown in Table 2,.

'iurious effect as the principal source of slime pro- T M duction hasbeen removed. Such a silica froth e 2 is then found to be quil'g1 stableshofivingma de- Sm Tamng cide tendenc for flocc a on of t e s ceousparticles in the? absence of slime. Feed 2:1 :85 Cationic The flotationof silica with the cationic reagent is so rapid anidaghe elicit; ofslime1 1217283685 gmmzgs mg)" l 80 3X 1 t from the non-floa le pc on soe e ous norms amoun that we prefer to remove the silica completely 50180mm above only i g fiig figzzggg g k 3: g fi ggg fg ig g The resultsset out in the above table are easily explained on the above theory thatthe cationic in fact cationic reagents generally, are rapid in te 1 h 1their promoter action, and in accordance with promo re Its w 0 6 p051 Ycharge idly to the silica. and then retains no further 1 the presentinvention we have found that 1mth t b d proved metallurgical results areobtained with charge so that e l amino recovere them if the time duringwhich the ore is and reused. It is practically 1mposs1ble to dejected tofroth notation is less than 20 seconds termme what goes on at theinstant of flotation The normal agitation and attrition produced 40 butthe above theory explams the factors set in the ordinary type ofmechanical or pneumatic out above easflv and we o o k ow or a y fltation cell produces a n amount of slime other theory of action whichwould explain the from the non-floatable portion of the ore so thatresults- Nevertheless t is P s e t other the more rapidly thenon-floatable portion is factor m y be present nd for his r son theremoved from the zone of agitation and attrition theory of action isadvanced only as a probable the more economically the silica can befloated e p n i n Wi t l mi ing the invention therewith smaller amountsof reagent. to.

The rapidity with which the sflica floats is a Broadly the presentinvention is not limited to further feature of the present invention andthe use of any p rti ar cationic p m r 88 permits the use of a singlecell or a relatively we have found that the interference of slime withsmall number 01 cells in place of a large string, silica flotationappears to be a general characthereby reducing equipment and powercosts. To teristic of cationic reagents. In addition to the show therapidity with which slime is formed by effect of slime which is theprimary feature of agitation within a flotation cell and its eflect thepresent invention, the prevention of conupon the flotation of silica weshow the followtinued contact of the cationic reagent with the ing tablewherein a phosphatic ore of the Florida flotation material both beforeand in the course pebble phosphate type is violently agitated with offlotation has a secondary advantage with a cationic active flotationreagent, dioctyl aminecertain cationic reagents of the aliphatic amineTable 1 Feed Non-float- 'Iafl- 23; 1 Reagents, B R L BeIBleL' Q1515. BIP F L' Rate Recov Eh-Md 52 235;

27.68 76.56 4.30 1.89 290 on .18 None 21.13 76.87 4.30 1.35 ass 90.9 .185

21.12 76.54 5.35 1.55 2.81 one .13

Th term none in the above table means that ype, which reagents are verysensitive to chemiair was admitted simultaneously with the start calchanges induced by the presence of air and of agitation, i. e., therewas no conditioning f water which are probably oxidizing and carbontheflotation feed before aeration. 7 ating phenomena although the exactnature has notbeendetern iined. Inthecaseofcationic reagents which aresensitive to air and water,

the present invention has the further advantage that no deteriorationdue to this cause can-take place as theperiod of contact betweenreagent. air, water and ore is almost instantaneous. The deleteriouseifect of agitation and aeration of the ore with water and a cationicactive flotation reagent, dioctyl amine is shown below in Table 3. 10

The data in the above table shows that di Table 3 Silica SecondsNon-float- Tail- Feed bk in oonosn- Rmo My Reagents. agitated n. P. L lmu lbs./t. feed and B. P. L- 1w]. B. P L at 28. 21 77. 41 4. 05 2. 12 2.99 95. 18 None 27. 96 76.16 B. so 1. 57 2.79 96. 3 .18 5 28. 31 74.996.8) 1.89 2.77 95.6 .18 B. 12 74. 64 7. 0o 1. 46 2. 74 96. 9 18 15 28.40 71.78 11. 10 1. 67 Out Out 18 Z) 27. 66 63. 04 2). 86 1. 14 Out Out18 The term none in the above table means that air was admittedsimultaneously with the start of agitation and the silica float. andphosphate tailing separated immediately, the froth being removed asquickly as it is physically possible.

octyl amine is stable unless in contact with air or slime.

25 The data in the following table show the effect of slime on theflotation of silica from phosphate rock using dioctyl amine as theflotation agent.

This is an added advantage of the present invention when sensitivecationic reagents are employed and is a feature which is included in amore restricted aspect of the invention.

A comparison of results in Tables 1 and 3 shows that the ore pulp andreagent can be agitated violently for 20 seconds before any deleteriousresults show up, whereas even 5 seconds of aeration start to show lossof reagent strength.

To show the effect of time alone on the stability of dioctyl amine, anemulsion of the amine It will be noted that even with one pound per tonof slime, or .044%, that the flotation is substantially killed. Even byadding a prohibitive amount of reagent it is impossible to float silicain the presence of slime. These examples show concretely the necessityof floating the silica at once before the flotation cell has time tomake slime.

The data in the following table show the eflect of increasing theamounts of amine reagent on the flotation of silica.

Table 6 Concentrate Reagent Frother 3.9% ffi i Ratio Reoov. 1bs./t.lbs/t.

B. P. L. Insol.

30. 96 33. 49 67. 05 5. 18 No stable froth 04 .05 31.05 54. 49 31. 50 3.34 N o stable froth .09 12 31. 49 69. 52 12. 2. 71 No stable froth l3 1731. 33 75. 43 5. 55 1.92 No stable froth l8 24 31. 66 77. 57 3. 2. 38 2.57 95. 4 22 29 31. 63 78.11 2. 50 2. 16 2. 58 95. 7 .27 .36 32. 24 77.79 2. 65 3. 04 2. 56 94. 3 .31 41 31. 93 79.30 2. 40 3. 56 2. 67 93. 036 48 31. 71 78. 75 2.05 4. 21 2. 71 91. 6 40 53 31. 43 79. 08 2.15 4.87 2. 79 90. 2 45 N representing a 40:1 mixture of dioctyl, aminesolvent and water was prepared. A portion of the fresh emulsionrepresenting .18 lbs/ton of ore was used immediately, to produce asilica float from a phosphate ore by adding directly to the ore pulpduring the flotation. A second portion of the emulsified amine was leftstanding in a closed container for 18 hours and an .18 lb./ton emulsionused in the same manner to produce a silica float.

The data is found in the following table.

65 The above tests were made with a typical cation 7 that it is notnecessary to the present invention to use ionizable compounds as similarresults are obtained with amines and with their ionized salts, providedsatisfactory dispersion and distribution is effected. The presentinvention is 75 therefore not intended to be limited in any way to theuse of a cation active promoter which is actually an ionizable compound.The interaction between the surface of the silica and the basic portionof the promoter does not appear to be tied up exclusively withthepresence of actual ions. The theory advanced in the Lenher patentreferred to above does not appear to be correct as applied to silicaflotation, or at least it'does not appear to be a necessary factor inthe present invention. For while Lenher is quite correct that all of thematerials which he describes in his patent and which are ionized areusable as silica promoters, and show improved results when used inaccordance with the procedure which forms the subject of the presentinvention, the improved results obtainable are not limited to thesematerials but the amines themselves which are in many cases notwater-soluble and are not accordingly ionized, behave in precisely thesame way. We do not wish to advance any definite theory of action insilica flotation and the present invention is not intended to be limitedto any particular theory of the Lenher patent.

From the foregoing examples it will be apparent to those skilled in theart that the flotation of silica can be accomplished almost instantly bythe improved process of the present invention, that fewer flotationcells can be employed to produce -a higher grade phosphate product andat the same time use a smaller quantity of flotation reagent.

What we claim is: 1 A process for separating by froth flotation asiliceous gangue from an ore containing a portion which is not readilyfloatable by promoters for silica flotation and which ore producesadditional slime under the ordinary agitation and aeration of a frothflotation cell which comprises desliming the feed, introducing the feedinto afroth flotation cell, adding a cationic silica flotation promoterdirectly to the deslimed ore pulp in the froth flotation cell withoutpreliminary conditioning, effecting froth flotation in said cell,removing therefrom a concentrate relatively rich in siliceous gangue,the time during which the ore pulp is subjected to froth flotation beingless than twenty seconds.

2. A process for separating by froth flotation a siliceous gangue froman ore containing aportion which is not readily floatable by promotersfor silica flotation and which ore produces additional slime under theordinary agitation and aeration of a froth flotation cell whichcomprises desliming the feed, introducing the feed into afroth'flotation cell, adding a cationic silica flotation promoter whichis subject to deterioration in contact with air and water directly tothe deslimed ore pulp in the froth flotation cell without preliminaryconditioning, effecting froth flotation in said cell, removing therefroma concentrate relatively rich in siliceous gangue, the time during whichthe ore pulp is subjected to froth flotation being less than twentyseconds.

3. A process for separating by froth flotation a siliceous gangue fromphosphate ore which ore produces additional slime under the ordinaryagitation and aeration of a froth flotation cell which comprisesdesliming the feed, introducing the feed into a froth flotation cell,adding a. cationic silica flotation promoter directly to the deslimedore pulp in the froth flotation cell without preliminary conditioning,effecting froth flotation in said cell, removing therefrom a concentraterelatively rich in siliceous gangue, the time during which the ore pulpis subjected to froth flotation being less than twenty seconds.

4. A process for separating by froth flotation a siliceous gangue fromphosphate ore which ore produces additional slime under the ordinaryagitation and aeration of a froth flotation cell which comprisesdesliming the feed, introducing the feed into a froth flotation cell,adding a cationic silica flotation promoter which is subject todeterioration in contact with air and water directly to the deslimed orepulp in the froth flotation cell without preliminary conditioning,effecting froth flotation in said cell, removing therefrom a concentraterelatively rich in siliceous gangue, the time during which the ore pulpis subjected to froth flotation being less than twenty seconds.

5. A process for separating by froth flotation a siliceous gangue froman ore containing a portion which is not readily floatable by promotersfor silica flotation and which ore produces additional slime under theordinary agitation and aeration of afroth flotation cell which comprisesdesliming the feed, introducing the feed into a froth flotation cell,adding a cationic amine silica flotation promoter directly to thedeslimed ore pulp in the froth flotation cell without preliminaryconditioning, effecting froth flotation in said cell,

removing therefrom a concentrate relatively rich in siliceous gangue,the time during which the ore pulp is subjected to froth flotation beingless than twenty seconds.

6. A process for separating by froth flotation a siliceous gangue froman ore containing a portion which is not readily floatable by promotersfor silica flotation and which ore produces additional slime under theordinary agitation and aeration of a froth flotation cell whichcomprises desliming the feed, introducing the feed into a frothflotation cell, adding a silica flotation promoter,

dioctyl amine, directly to the deslimed froth flotation in said cell,removing therefrom a concentrate relatively rich in siliceous gangue,the time during which the ore pulp is subjected to froth flotation beingless than twenty seconds.

7. A process for separating by froth flotation a siliceous gangue froman ore containing a portion which is not readily floatable by'promotersfor silica flotation and which ore produces additional slime under theordinary agitation and aeration of a froth flotation cell whichcomprises desliming the feed, introducing the feed into a frothflotation cell, adding a silica flotation promoter, lauryl amine,directly to the deslimed ore pulp in the froth flotation cell withoutpreliminary conditioning, effecting froth flotation in said cell,removing therefrom a concentrate relatively rich in siliceous gangue,the time during which the ore pulp is subjected to froth flotation beingless than twenty seconds.

8. A method according to claim 3 in which the phosphatic ore is Floridapebble phosphate.

9. A method according to claim 4 in which the phosphatic ore is Floridapebble phosphate.

10. A method according to claim 1 in which the flotation is effected ina single rougher cell followed by cleaning of the silica concentrateproduced.

11. A method according to claim 3 in which the flotation is effected ina single rougher cell followed by cleaning of the silica concentrateproduced.

HARRY L'. MEAD. ERNEST J. MAUST

